Method to Avoid Star Point Data Reflections

In a network of three or more transmission lines connected together at a common "star" point, signals encounter a large transmission discontinuity that impairs communication. Part of an incident signal is reflected backward and the remaining portion is split amongst the outgoing lines. For example, when 6 lines with equal impedances are connected together, ongoing signals are attenuated by 9.5 dB. Reflections can be mitigated by adding series matching impedances to each line at the star point but this increases ongoing signal attenuation to 14 dB for the example of 6 connected lines. We present a method where negative impedance is applied to the star point to simultaneously reduce signal reflection and attenuation. The paper initially considers coaxial transmission lines with equal impedances and shows experimental results for baseband pulse transmission. Stability is a concern when adding negative impedance and accurate knowledge of line impedance is required. The paper concludes with a discussion on impedance compensation at a building breaker panel where transmission line impedances vary widely and are a function of frequency